How moving your eyes in a specific way can help you solve a complex problem without even realizing it

Blogging on Peer-Reviewed Research

Can you solve this problem?

Given a human being with an inoperable stomach tumor, and lasers which destroy organic tissue at sufficient intensity, how can one cure the person with these lasers and, at the same time, avoid harming the healthy tissue that surrounds the tumor?


For the solution and evidence from Laura Thomas and Alejandro Lleras (2007) that shows that moving your eyes in a specific way can help you solve the problem, continue reading after the break.

In the 1940's and 50's gestalt psychologists began to study what they termed insight problems, where once a crucial element of the problem is discovered people achieve the AHA! moment of sudden insight. One of the most famous of problems was the Karl Dunker Radiation Problem highlighted above. The solution to the problem requires the critical insight that you can shoot multiple low-intensity lasers from different places around the body so that they can converge on the tumor and destroy it without damaging skin that a single high powered laser would.

So what do eye movements have to do with this problem you ask?! This is where it really starts to get cool.

Eye-tracking research by Grant and Spivey (2003) showed that people who spontaneously solved the problem without any hints looked more often at the skin crossing area and made significantly more in-and-out eye movements radiating around the entire body than those who weren't able to solve the problem or required hints. This is called embodied cognition, or in other words some part(s) of your body reflects an internal mental process externally.

Thomas and Lleras (2007) wondered whether eye movements are just a reflection of internal problem solving or whether changing peoples eye-movement patterns could lead to more successful problem solving. With the knowledge that people solved the radiation problem more effectively when they made triangular crossings between the tumor and the skin Thomas and Lleras constructed a task that had participants making different patterns of eye movements during an unrelated task in which they had to follow numbers around the screen as they appeared (see the figure below).


What they discovered was that in the condition where participants made movement in and out of the body in a triangular fashion (figure B above), they successfully solved the radiation problem more frequently.


What's even more amazing about this result is that the participants did not even realize that their eye movements were contributing to their solving the problem. In fact, according to the researchers, "many believed the tracking task was a purposeful distraction from the radiation problem."

According to a press release from the Beckman Institute at the University of Illinois

"The theory that we're working with right now is the idea that when people do these sorts of movements it actually starts them on what's called a perceptual simulation," Lleras said. "The idea is that you basically use the same structures in the brain when you are thinking about doing something that you would actually use when you do that task. So we start them on this movement and that starts this simulation of how to solve the problem."

This of course is the quick and dirty final result - many other ways of analyzing the results are in the paper which is available here. I highly recommend reading this interesting paper in full! After all anyone who uses this really cool eye tracking setup has to do awesome research:


This is a report on: Thomas, L.E., & Lleras, A. (2007). Moving eyes and moving thought: On the spatial compatibility between eye movements and cognition. Psychonomic Bulletin & Review, 14, 663-668.


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ERICA is a lot cooler eye-tracking interface. It uses a small IR camera and light mounted on the display and watches for the reflection of the IR clint with respect to the circle of the pupil -- You don't have to bolt your face into anything.

This reminds me of a study which I cannot find at the moment showing that recall or insight problem solving is improved when subjects make frequent left-right saccades. The argument was that this improved interhemispheric communication, consistent with other evidence that insight solutions are accompanied by increases in long-range synchrony. This alternative does not seem to be considered here. I realize that in the absence of a citation, this alternative explanation seems absurd. I'll keep looking. Anyone else remember this study? Published in the last 18 months I think.

Hey Steve - you have to admit the trend is in the right direction for C's results, AND that the number of left-right saccades which cross midline in C is much less than the number in B. So I think this alternative is still very plausible, and maybe eve more plausible, since it the trend where C provides intermediate performance.

Damn, I wish we could edit comments. I meant to say that the left-right hypothesis explains the trend where C supports intermediate performance, but now I realize it's actually repeated skin crossing which is intermediate (the dotted lines can be difficult to distinguish). I can be sneaky and say that involves a lot of left-right saccades too. Anyway, until we find the citation it's possible I'm making all this up. lol :)

Found it but it has to do with improvements in veridical recall and decreases in false recall in a DRM paradigm. Maybe irrelevant here.

I don't find that very plausible, CHCH. Moving our eyes from left to right improves inter-hemispheric "communication" and "enhances" (somehow) our problem-solving ability?

This experiment is better explained by embodied cognition and perceptual-motor theories. I haven't read the reprint yet, but probably people are mentally "doing" or "acting out" things when they are moving their eyes. This primes the correct solution, in the same way this other study did, in which people physically acted out things and showed better analogical transfer:

See also Alva Noe's book Action in Perception, and related work in embodied cognition (reviewed in a book by Raymond Gibbs).

Hi Doug - Your scare quotes reflect your lack of knowledge. The "enhancement" due to horizontal eye movements has been statistically confirmed in recall (read the study I linked to).

Also, are you unaware of the pheomenon of interhemispheric communication? Look up split brain patients and the corpus callosum, and then look up optic motor apraxia (related to failed horizontal eye movements) and the association with by callosal agenesis. Then I'll be interested in what you find plausible.

There needs to be more info provided in the question -- we can't assume that it's only the cumulative effect of the laser that zaps the tumor. If I want to deafen someone who's in a circular room, I don't send a million people to gently tap on the walls. A person isn't blinded by low-intensity light coming from myriad sources. And so on...

no, you can't assume that, but is what happens if high-energy radiation is used. in fact, it is the basis of treatment for cancer with radiation (it's the physics ya see).
the sound analogy is not apt as sound energy is a different phenomenon.

The sound analogy is apt, given that you can't assume knowledge of physics and cancer on the part of the test-taker -- in fact, my first physics thought was the Photoelectric Effect, and that's why clarification is needed.

Unless the test was given to students who knew how cancer radiation works already.

the PE effect is one of the x-ray interactions that occur but is most likely not the mot important in the energy range for cancer treatment. compton is generally more important. nonetheless ... it is a cool study

Aren't we complicating things here? Doug Holton basically said it, 'We are acting out what the lasers are to do.' The problem and its solution is meant to correlate with such persons' B eye movement. If the solution was to say zap the tumor with one laser from above than I would dare to guess group D would be statistically higher in correctness.

is a lot cooler eye-tracking interface. It uses a small IR camera and light mounted on the display and watches for the reflection of the IR clint with respect to the circle of the pupil -- You don't have to bolt your face into anything.